Suction fan unit



May 26, 1942., J. M. FUNK sucuon FAN UNIT 2 Sheets-Sheet 1 Filed July 25, 1940 ay 26, 1942., J. M. FUNK 2,284,141

SUCTION FAN UNIT Filed July 25, 1940 2 Sheets-Sheet 2 Patented May 26, 1942 maxim:

- 1 umrao STATES PAT "1. o-F. :j1 .g j v A 2,234,141 SUCTION FAN UNIT James M. Funk, Ottawa, 111., assignor to Advance Aluminum Castings Corporation, @hioagoylih,

a corporation of illinois I Application July 25, 1940, .Seriallilo. 347,323

' Claims. (01. zoo-11;) g

This invention relates to a suction fan unit and is particularly concerned with the provision of a unit in which the 'fan is so designed that the motor for driving 'the same canbe housed with .-the fan inside the cabinet for compactness andneat appea "ance as-well as to enable use of theunit in many installations where an exposed motor-would be objectionable, if not entirely out .of the question.

The suction fan unit of my invention, as will hereinafter appear, provides pressure resisting characteristics of the centrifugal blower type of fan without requiring the scroll housing or auxiliary apparatus for its functioning and, in relation to a blower unit of equal capacity, is less costly, smallenin displacement, and, while no greater in rotational speed, :is despite its smaller displacement equal in efficiency, in addition to having better eye appeal and being equallyquiet in operation.

The present suction fan, in accordance with my invention, is intended to operate in close confinement with other mechanisms which a given installation may. dictate the necessity or desirability of installing within the same cabinet structure, along with the motor for driving the fan.

The invention is illustrated in the accompanying drawings, in whichthe .inventionis not limited .toan arrangement wherein the motor .H is supported on the bottom wall of the cabinet. It should alsobe understood that while there is .only the motor I I shown the suction fan unit of my invention. As a matout air cooling.

flow is indicated by ,the arrow l5 in Fig. 1, this Fig. 1 is a, longitudinal section through a suction fan unit made in accordance with my invention showing the motor in side elevation and the fan in cross-section;

.Fig. 2 is an intake face view of the fan, and

'Figs. 3 and 4' are views similar to Figs. 1 and 2,

but showing a modified or alternative construction and showing only a portion of the cabinet in Fig. 3 to conserve space in the drawings.

JSimilar reference numerals are applied to corresponding parts throughout these views.

Referring first to Figs. 1 and 2, the numeral 5 designatesthe face plate forming one wall of a cabinet 6 and having an outwardly curved circu. lar flange l defining a circular air inlet opening d. An air outlet opening is indicated at 9 in the back plate it, but it should be understood that the invention is not limited to' this specific ar- Ian'gement'of the inlet and outlet'with respect to the electric motor H and suction fan i2 driven thereby, although, of course, the specific relationship of the inlet 8 to the fan i2 is important.

as well as the arrangement .of the motor H in side the cabinet-d, as will soon appear. The motor H is mounted on a suitable resilientsupporting bracket I3 fastenedto a-wall-of the cabinet 51, :as .:shoyvn, but .it must be understood that ter of fact, in certain types of installations these other devices require the protection of the cabinet 6 where the suction fan unit is used in a high temperature zone. In other words, the air flow through the cabinet keeps the motor H, as well asthe auxiliary device. or devices, indicated diagrammatically in dotted lines at Ila, from. reaching excessive temperatures.

Thus, in one type of installation the housing of the other devices in .the cabinet means improved appearance,

while in the other installations it enables operation ofthese other devices as well as the motor H in a zone of higher temperatures where these devices and the motor would otherwise be incapable of operating for any length of time with- The general direction of air approximates the usual working pressures in stokers, oil burners, and air conditioning apparatus in general. The resultant direction of .flow is changed from axial to radial with an increase in downstream resistance to flow; that is to say, the flow of air will be more in an axial direction as the quantity of air flow is increased and in a radial direction-as the flow is decreased to a minimum, at which time all of the energy imparted by the fan l2 to the air is static pressure. The fan 12 is carried by its hub 16 on the shaft It .and. has a convexo-concave or generally conoidal form' of back plate ll preferably cast integral with the hub and carrying impeller blades-l8 on its outer face and projecting'beyond the periphery to theextent shown. The purpose in having the diameter of the back plate less than the outside diameter of the blades is to permit air flow in an axial direction past the back plate, as shown at 15, and to increase the flow rate and the air handling capacity of the fan. The exact diameter of back plate required in relation to blade tip diameter is governed by the static pressure which it is desired to build up' in the cabinet 6 and required to overcome resistance to flow through the cabinet. The back where the peripheral velocity convertedto pressure in accordance. with well known fan laws equals therequired operating pressure in the cabinet. The location of the motor II in. the immediatedown'stream area of the fan I! has been found by experiment to be most important to secure the desired performance, there being no air flow directed to the space occupied by the motor so that in the absence of the motor there would be eddy currents at this point and accordingly a marked loss in efllciency by reason of the energy in the stream being partly expended in the void behind the fan. It is evident therefore that the presence of a structure like the motor II 'in the low pressure area filling what would otherwise be a void and forming streamlined surfaces for the air flow past the same results in a,ae4,14i

.reaching radially beyond the periphery of the plate diameter is increased for higher static pres sure in the cabinet, that is, the back plate is exctended out to a larger diameter in the circle swept out by the blades until a point is reached a fan performance nearer to blower performance. For the same reasons the upstream or outer surface of the back plate ll is streamlined, and these surfaces are brought as close as practical to the tips of the blades l8, turbulence being thereby avoided and the operating efiiciency of the fan increased. The streamlined shape of the back plate ll aids air flow in an axial direction, and turbulence and shock noises with consequent loss in eiiiciencyof operation are avoided. The diameter of the inlet opening 8 in relation to the diameter of the fan 12, the closeness of the fan I 2 to the inside of the face plate 5, the radius of curvature of the inlet flange l, and having the upstream edge of the inlet smaller in diameter than the diameter of the downstream edge, all in combination and in the relationship shown, have been found to give the best performance in the various units tested under ordinary working conditions. The impeller blades l8 may be classified as forward curves" but set at a.back angle in relation to the direction of rotation. .As indicated in Fig. 2, the radius [9 of curvature of the .blades I8 is equal to approximately .59 of the fan radius, while the angle 20 for the blade setting is approximately 31 back from points at .5 of the radius of the fan, seventeen. impeller blades being employed with the blades set parallel with the axis of rotation. However, a change in the number of blades or their axial length it must be understood will change the fans capacity according to well known fan laws, and such changes are anticipated in order to suit more nearly the exact requirements of each fan installation. Such changes in blade design and angle may be made without departing from the present invention, the present disclosure being merely a specific combination of fan variables which have been found to meet the requirements best for a certain installation.

The unit shown in Fig. 3 has afan l2a driven by an electric motor ll housed with the fan inside the cabinet 6 with a view to obtaining generally the same advantages as above pointed out regarding the unit of Fig. 1. The fan Ila, however, has'a fiat back plate Ila preferably cast integral with the hub I60. by means of which the fan is mounted on the armature shaft 14 of the motor. The impeller blades Illa in this fan are also preferably castv integral with the back plate and project from the upstream face thereof,

back plate to approximately the same extent as the impeller blades ll of the fan I2 in relation to the back plate l'l. With this construction, 'the air flow is substantially in the direction of the arrow lia. -While the unit of 'Fig. 8 will operate satisfactorily, although" not with the same high efficiency as the unit of Fig. 1, the principal difference lies in the fact that the flat back plate I'Ia does not permit of such compactness of assembly as the streamlined back plate ll. Here again the motor ll fills the void in the downstream area behind the back plate so that turbulence and consequent loss in efflciency of operation of the unit is avoided.

It is believed the foregoing description'conveys a good understanding of the objects and advantages of my invention. The appended claims have been drawn with a view to covering all legitimate modifications and adaptations.

I claim:

.1. In combination, a suction fan comprising a substantially circular back plate having means at the center thereof for driving the same, and impeller blades projecting in an axial direction from the upstream face of said back plate and also in a radial direction beyond the periphery of said back plate, and a cabinet having a circu- 2. In combination, a suction fan comprising a a substantially cir'cularback plate having means at the center thereof for driving the same, and impeller blades projecting in an axial direction from the upstream face of said back plate and also in a radial direction beyond the periphery ofsaid back plate, the blades being forwardly curved and set at a, backward angle with respect to radii of said back plate in relation to the directionof rotation, and a cabinet having a circular air -inlet and an air outlet, the fan being disposed inside said cabinet in proximity to said inlet with the upstream face toward the inlet and in substantially coaxial relation thereto, the inlet being of a diameter larger than the diameter of the back plate but substantially smaller than the tip diameter of the blades, the air flow induced by the fan from the inlet to the outlet being generally in an axial direction between the iilmzeller blades pastthe periphery of the back p a e.

3. In combination, a suction fan comprising a substantially circular back plate having means at the center thereof for driving the same, the back plate having a concavo-convex form, the convex face being the upstream face, 'and impeller blades projecting in an axial direction from the upstream face of said back plate and also in a radial direction beyond the periphery of said back plate, and a cabinet having a circular 8.11 inlet and an air outlet, the fan being disposed inside said cabinet in proximity to said inlet with the upstream face toward the inlet and in substantially coaxial relation thereto, the inlet being of a diameter larger than the diameter of the back plate but substantially smaller than the tip diameter of the blades, the air flow induced by the fan from the inlet to the outlet,

being generally in an axial direction between the impeller blades past the periphery of the back plate.

4. In combination, a suction fan comprising a substantially circular back plate having means at the center thereof for driving the same, the back plate having a concavo-convex form, the convex face being the upstreamsface, and impeller blades projecting in an axial direction from the upstream face of said back plate and also in a radial direction beyond the periphery of said back plate, the blades being forwardly curved and set at a backward angle with respect to radii of said back plate in relation to the direction of rotation, and a cabinet having a circular air inlet and anair outlet, the fan being disposedinside said cabinet in proximity to said inlet with the upstream face toward the inlet and in substantially coaxial relation thereto, the inlet being of a diameter larger' than the diameter of the back plate but substantially smaller than the tip diameter of the blades, the air flow induced by the fan from the inlet to the outlet being generally in an axial direction between the impeller blades past the periphery of the back plate,

5. In combination, a suction fan comprising a substantially circular back plate having means' at the center thereof for driving the same, the back plate having a concave-convex form, the convex face-being the upstream face, and impeller blades projecting in an axial direction from the upstream face of said back plate and also in a radial direction beyond the periphery of said back plate, a cabinet having a circular air inlet and an air outlet, the fan being disposed inside said cabinet in proximity to said inlet with the upstream face" toward the inlet and in substantially coaxialfirelation thereto, the inlet being of a diameter larger than the diameter of the back plate but substantially smaller than the tip diameter of the blades, the air flow induced by the fan from the inlet to the outlet being generally in an axial direction between the impeller blades past the periphery of the back plate, and a motor for driving said fan disposed downstream with respect to the back plate in substantially concentric, relation thereto and operatively con- JAMES M. FUNK. 

